Introduction

Runes

Summoner Spells

AP Garen has a weak early game, so it's wise to take teleport or revive so you can get back to lane quickly as deaths during laning phase can be frequent.

Garen also has the smallest mana pool in the game, clarity is essential.

Items

Ap Garen revolves around Deathfire Grasp, which enables his ult to do stupid amounts of damage. Other magic penetration items will help you as well. At some point in the game, remember to buy a Lich Bane so your auto-attacks can bring Demacian Justice to your enemies as well.

Finally, Garen has a notoriously low mana pool, in addition to your clarity summoner spell, one must always have a decent supply of mana pots. You can never have enough.

Unique Skills

Virtually anyone and everyone under 75% hp can and will die in your presence if you manage to get built.